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How much do 1947 and 2014 Beechcraft Bonanzas have in common?
A question about the tail shape of the Bonanza and Oldest aircraft still in production led me to wonder how much the first and latest aircraft in this series actually have in common.
1947

 lost flights
2014
 Beechcraft
 AOPA
Clearly the following have changed

tail design
number of windows
engines
internal arrangements for seating and baggage
detailed changes to wing shape
cockpit instrumentation
cockpit controls

and many other changes
Is the basic central-airframe and core-wing design and construction identical?
Are there any parts in common - or at least directly interchangeable?

The rudder pedals still look the same :-)

Too much. Rumor has it that the wing spar could profit from some local reinforcement to make the wing more forgiving of short trips outside of the envelope, but lawyers will immediately jump on this as proof of admission of guilt by Beech. So the wing spar remains unchanged and the Bonanza less safe than easily possible.

FWIW, the tail design is actually the same - it's the same panel, but bolted on 3 times instead of 2, and at different points.

@egid, the vertical is clearly different, so it's still two times.

@JanHudec Sorry, this was 3 years ago, but I believe I was talking about the first conventional tail 'Bonanza' design, which is the T-34 (1948). The same tail shows up on the Travel Air.

The V-Tail Bonanza design was retired (for a bunch of reasons, many of them marketing-related), but the actual airframe of a modern Beech 36 Bonanza is, essentially, the same as the 1968 Beech 36 (and very similar to the 1959 Debonair, just stretched). You can trace a great deal of the design and parts back to the V-tail as well.
There have been some changes made to the design over the years (for example, the throw-over yoke is gone, replaced by conventional dual controls), but the bulk of the airframe parts are interchangeable because the designs are essentially the same (this is an advantage for Beech owners: The factory is still producing nearly all the parts you'll need for maintenance, because they need them to put in the new planes).

Most of the light GA aircraft produced by the legacy manufacturers (Beech, Cessna, Piper) are what are known as "follow-on type certificate models" -- they are the same production design approved back in the 1950s/1960s, with "minor" changes incorporated along the way. This means you'll find the same kind of parts continuity in pretty much all the major manufacturer's aircraft:

Most of the parts on a 1960s Cherokee 180 are the same parts you'll find in a 2014 Archer III (changes to the airfoil and panel layout notwithstanding)
Many of the parts on a modern Cessna 172S are the same as the 1965 172F (the year they went to electric flaps).

You'll find many common parts on the 172 going back all the way to the original 1956 172 if you look. Big changes were the swept-back tail fin (1960) and the electric flaps (1965)


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What is this button (pressed during approach) on the Airbus A320?
I was watching a YouTube video of a cobalt air a320 landing and I seen as he was about 2000 ft AGL he pressed a button on his right hand side just beside the Navigation display. The button illuminated green and 10 seconds later he pressed it again to 'disengage' it.

Does anyone know what this could be and why it is used?

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Has any passenger airliner ever offered forward-facing windows?
The empty, dolphin-like, forehead of the A380 seems like it would be an amazing place for the first and/or business class bar, especially if it had forward-facing windows.
I realize in the A380's case there are crew rest and storage compartments in that space, but wondered if there have ever been any passenger planes outfitted with forward-facing windows to enjoy the view?

Image source: lufthansa.com

Not a complete answer, but there were plans to build a plane with a viewing dome on top of the fuselage. I haven't heard anything more about it so I'm guessing that, unsurprisingly, it was never put into production.

Probably because of the cost, weight, and structural complications that large windows entail. Party Ark's examples are all older aircraft that fly lower and slower than modern ones.

Other than takeoff and landing, is the view from the front that much better than from the side? Enough to pay for the high cost of building it? During takeoff and landings, no one would be allowed in the view lounge anyway, so seems like the most interesting view would be wasted.

I have heard recently of aircraft offering rooms with virtual windows (using fibre optic cameras to get an outside view, not sure how they make up for lack for viewing angles!), but building on that you could add front facing  views!?

The view from the front is always better.  It stinks to have to sit facing sideways, craning your neck to see out a little porthole that always seem to mounted too low (or the seats are too high), especially around someone else's head. I have flying commercial for that reason, vs flying my own plane.  All the way across the US for business I don't really have a choice, but I never look forward to it.

From my limited experience of commercial flight, it seems that the great majority would rather watch in-flight TV than look out the windows.

There is a story about a wide-body (not sure if it was a 747 or a DC-10 or variant) commercial jet with a forward-mounted camera that would be shown on the screen in the main cabin during takeoffs but the practice was discontinued after one of the planes crashed after a takeoff and they realized the passengers watched the whole thing live.  While it could be apocryphal, I'd appreciate if anyone could verify or debunk the story, either way.

Amtrak has Dome Cars (they are holdouts from the 1950s, maintained for their scarcity) that have forward views.  They, too, are closed during takeoff and landi-- I mean initial departure from origin station and approach to terminus.  The modern equivalent is the Superliner Lounge Cafe, which is pretty much huge windows floor to ceiling. Pressurization? Not gonna happen.

We could start with the Tupolev ANT-20 with its rather daring forward-facing passenger gallery. [edit - the prime seat right at the front in the gallery was for the navigator and his equipment.]

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Like the Tupolev, most examples are inter-war. Here is the moderately successful Latécoère 521 being assembled showing its gallery beneath the cockpit [edit - seems this was only for the navigator, not for passengers] :

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... and the more esoteric Caproni Ca.60 which would have made for an interesting journey had it entered service -

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-- EDIT - one special mention for the Junkers G.38 which also had a sizable glazed area in the wings. Unfortunately as far as I can tell (and despite what Wikipedia says) neither the nose nor wings were accessible by the passengers, but rather used by the navigators and engineers, which seems like a missed opportunity. [ed. the wing area was indeed intended for passenger, see comments]

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I was wondering why the Caproni Ca.60 looked familiar before I realized: Hayao Miyazaki animated that amazing aircraft in his film The Wind Rises.

Did the ANT-20's flight pilot/etc share the nose with the passenger gallery, or were they in the pod structure on the top?

@DanNeely the cutaway isn't brilliant, but it and the photo do show the cockpit area above and behind the gallery in a fairly conventional manner. The pod on top of the upper engine is not, despite appearances, for a person, but part of the cooling for the engine. There's a better cutaway here - https://www.flickr.com/photos/x-ray_delta_one/6986518667

thank you.  That picture was clearer, or was after I went into the page source to find the full res version.  For some reason Flickr was only showing the lower res version even though it had a better one available.

Interesting aircraft. I suppose any examples of this features would be pre-1970s, before they realized that having actual seats with paying passengers was really the best way to go.

It's good to have a healthy skepticism for Wikipedia, but maybe you trust NACA aircraft circular 116 more. The wing of the Junkers G-38 held six passenger seats, three on each side. The walkway for engine inspection was behind the forward passenger cabin.

Thank you that was really fascinating. While I agree that this was the design intention, I'm sceptical it would have been much used: to get to the leading-edge cabins from the passenger cabin, you'd have to clamber through the area marked 'passenger, freight, tanks etc.' in Fig 1, which the NACA report states would be where you'd put all the luggage ( https://c1.staticflickr.com/7/6110/6326590078_21c8fb58c8_b.jpg ), and then through the engine inspection doors. Which might have been a bit much for a refined passenger. On the other hand, who'd want to miss an experience like that?

Here's a contemporary artist's impression. While there are a few errors, it does give a good idea of how the G.38 was divided, and the only view I've found of what it might have been like to be inside the wing as a passenger  - https://4.bp.blogspot.com/-T0l0zPeCTcs/V450-_X3rXI/AAAAAAAArA8/FssZzrJhv9cqWhQja8FNW9XfB037iRz-wCLcB/s1600/11.png

@PartyArk Speaking of artist's impression of the (inside of) the G.38 , I think it's worth mentioning "The wind rises" (animated movie from Miyazaki)

Boeing 747
I'm a little surprised to not already see the Queen of the Skies here. If 'partially forward' counts, the first several windows on each side of the lower deck of the 747 are angled partially forward. The angle is enough that passengers seated in the first row or so can indeed see directly in front of the aircraft.

KLM 747-400 Front View - Image Source: Wikipedia
Many 747 operators choose to install First or Business class seats in the forward part of the lower deck. Especially with some of the "reverse herringbone" style business class configurations, where the seats are angled relative to the cabin wall, this can result in the first row or two facing more-or-less straight forward with a window in front of them. This was the case with Delta's 747-400 configuration, for example. The 747 is notable as one of the few, if not the only, modern airliner to offer such a view to passengers through an actual window (as opposed to camera views on the IFE screens.)
Of course, there aren't any windows facing directly forward on the lower deck, as that would require placing them on the front of the nose itself, where the radome is.

That would definitely be an appealing feature for passengers but the airframe of the A380 at its forehead is too curved to be able to fit a viewing area for passengers.   Furthermore, the design and operational (aerodynamic) costs associated with structuring an aircraft to be able to fit a cockpit and a forward viewing area, along with the cost of another set of cockpit-spec windows has economically ruled out such a feature for modern airlines competing in a market where ticket price rules all.
I would imagine airlines would opt to install remote viewing stations connected to external cameras before creating a space with forward facing windows.   In fact, some airlines have already started to do just that -- Etihad's First Class "Apartment" seats have monitors that are connected to cameras with different viewing angles outside of the plane.
Many Soviet passenger aircraft did in fact have viewing areas in the nose of the aircraft aside from the cockpit.   Unfortunately for travelers, these areas were designated for navigators, not passengers.   Some examples:
Tu-104:

Tu-134:

An-12:

The scumclass seat I was allocated on my Cathay Pacific flight from Hong Kong to Auckland (in Q1 2018) also had cameras accessible via the seat mounted monitor. We had great fun watching approach and landing.

Those Russian aircraft look like convertible bombers.  That "navigator" position in the nose looks a lot like the bomb sight compartment.

@Gusdor Same with my Qantas A380 flight earlier this year; the in-flight entertainment screen (even in coach) had an option to see a feed from a camera mounted on the upper forward part of the tail.

@bogardpd The cameras are on the 777-300ER, A380, and at least some A350s.

@Gusdor reminds me: on a recent Emirates flight a radio program about the Dubai World Expo featured a speaker about future of airplanes. He suggested that eliminating windows altogether and replacing them with cameras and screens would save 1/3 of fuselage weight, allowing for faster flight/ shorter trips at same fuel cost

Usual feature nowadays, I think this is standard for all new planes since release of the A380, the new B747-8 also features this. Lufthansa just hides this pretty good in the board-entertainment of all classes, at least in 2014.

@Peter The 777-300ER had it even before the A380. It was added to assist the pilots in taxiing, but several airlines also attach it to the IFE system for passengers to view.

@reirab: Good to know. And it is smart! Hope the smaller new ones (A320Neo and B737Max) will get this also, but even if, IFE is there seldom :(

@Peter Yeah, it would be nice to have it on narrow-bodies, but it's not really a need for the pilots in those cases, so it hasn't been as much of a priority to add it. It would mostly just be for passenger entertainment on those aircraft. As far as the presence of IFE is concerned, all of Delta's A320s and 737s have IFE now, as far as I know. Unfortunately, it's not as common with other carriers... and some carriers are even removing it. Many carriers do have streaming over the in-flight Wi-Fi, though.

@MikeBrass Good point - I don't think they were designed to be 'convertible' bombers, as the following post explains, but I agree that this design choice was probably linked to bombsight compartments.  The navigator position was in fact important because navigation at the time in Russia relied a lot on ground reference: https://aviation.stackexchange.com/questions/24115/is-the-glass-nose-tu-134-design-for-easier-conversion-to-military-use

Another two examples from the Farman Aviation Works, purveyors of the world's ugliest aircraft. Unlike the ANT-20 (the gallery primarily for the navigator), the Caproni (never operational) and the Junkers (where the wing pods are separate from the passenger compartment), the Farman F.120 and the F.60 "Goliath" were designed with the full gallery experience in mind.
The forward view in the Goliath was interrupted on the left hand side of the fuselage by the walkway up to the exposed cockpit on top. However, the F.120 had, I think, exactly what is being asked for - uninterrupted forward view for the passengers.

F.120 interior
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F.120 in flight (also known variously and confusingly as the F.3X and F.4X)
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"This unidentified horse accompanied Miss Betty Rand and the Hamm brothers from London to Paris aboard the Farman F.60 Normandie in 1922."
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Look! Herringbone seating! And Branson claimed he had a patent on it! :)

That F.60 looks like a tramcar with wings.

+1 for wicker chairs on an aircraft

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How much fuel is used for the different phases of the flight of a typical airliner?
An Airliner flies from LA to JFK in 5 hours. In the first 30 minutes the plane climbs to about 30,000ft. For the next 4 hours the plane flies at about 30,000ft. For the next 30 minutes the plane descends to JFK.
What % of the total fuel used for the flight is consumed in each of the 3 phases  of the flight, i.e, the climb out, the cruise, the descent?

You forgot the 4th phase, at JFK: waiting 1 (or 2) hours to get a gate... Needs some fuel too, to keep passengers warm.

From this site by Boeing for the B737-800: fuel used for TO and climb = 2,300 kg.
From this site: fuel burn in cruise for B737-800 is 2,500 kg/hr
From this site: fuel burn at idle of a CFM56 engine = 300 kg/hr, so for the half hour descent two engines burn through 300 kg.

Total fuel for a 4 hour cruise flight is therefore 2,300 + 4 * 2,500 + 300 = 12,600 kg. Percentages:

TO & Climb =  19%
4-hour cruise = 79%
30-minute descent at idle: 2%

Interesting how close my estimations were to those values.

I know pretty nearly nothing about airplanes, but I do fly a lot. Surely the "landing" phase has to take significantly more than that 2%—flaps come out about 10 minutes before landing, and engine revs go up significantly. Once the plane actually lands, engines go on full power for braking. And then there's the obligatory circling at low altitude over Heathrow...

@Auspex Yes, you do not land with engines at idle. You want some engine power to control descent rate and increase safety if you cannot land.

Fuel savings due to higher TAS at cruise altitude does contribute to fuel economy, adding validity to the sourced data.

@757toga Thanks for that. I'd never have imagined braking was such a low percentage of full power. I guess it just sounds more powerful.

This one varies based upon selected power settings during climb, atmospheric conditions, aircraft loadout, winds aloft, etc.  you would have to consult the performance tables in the operators handbook in question for this one.  A good estimate would be about 85% of the total fuel consumed would be done during cruise flight, with around 10% used during taxi, takeoff and climb and about 5% consumed during descent.

And of the 10% fuel used until cruise altitude is reached, roughly half (5 %) is used for altitude gain, no? (rest contributes to horizontal progress towards destination).

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Why aren't there brake lights on aircraft?
Why don't aircraft have brake lights so you can see when an aircraft in front is slowing down?
I know there are air traffic controllers to control aircraft but they cannot do much about an aircraft's speed on the ground, it is down to the pilot.

Question in reverse: why aren't there Navigation lights on automobiles. The reasons are the same : "To avoid collisions"

@Mazura Brake lights are so other vehicles know that you're about to slow down or stop, possibly very quickly. Headlights, tail lights, and parking lights are the road vehicle equivalents of navigation lights. Turn signals, brake lights, and backup lights don't really have equivalents on aircraft because they're generally not needed. Airplanes don't taxi quickly, nor do they stop or turn quickly while taxiing. Also, most aircraft moving on the taxiways are in radio communication with each other, so they frequently already know each other's intentions.

Four words, not an answer because it would be a circular argument: steering via differential braking.

'cause where we are going, there are no roads.

They simply aren't necessary.
Brake lights are on road vehicles because often they travel at relatively high speeds, and follow relatively close to one another. If a driver suddenly slows, the brake lights help provide a visual cue (which grabs the attention of other drivers, and is visible from quite a long distance) that the vehicle intends to slow or stop.
In aviation, no aircraft should be traveling on the ground (taxiing) at such a velocity that stopping in a short distance is a problem - nor should they be following another aircraft too closely (regulations/airport rules govern both taxi speed and following distances). Taxiing aircraft are either in communication with an air traffic controller, or each other, making the need for sudden stops, change in speed or direction highly unusual. In addition, there is a higher degree of professionalism within the aviation community than your ordinary automobile driver; pilots pay closer attention to what their and other aircraft are doing; i.e., you won't find a pilot with a Big-Gulp in one hand, a shaving razor in the other, head facing the back seat passengers, all while attempting to pilot the aircraft!
In short, brake lights wouldn't be necessary on road vehicles either under the same conditions - but as it is, they assist in preventing collisions in numerous situations. In aviation, these sorts of collisions do not occur often due to the factors above, and therefore are not necessary.

I would dispute the last paragraph, but +1 for the first part. The stopping distance of a car is much, much, much, shorter than that of an aircraft. The speed limit on the highways near where I live are faster than the speed at which I land, but I can stop from that speed far more quickly in my car and the car behind me will be much closer. If I suddenly need to stop immediately (say, a deer suddenly decides that the highway would be a great place to stand,) the car behind me will have a fraction of a second to respond to keep from hitting me, even without distraction.

@reirab I don't think brake lights would have any effect for landing aircraft... you just can't stop from those speeds, as you mentioned, and ATC should be in control of any runway incursions as well as landing planes are required to determine if the runway is safe to land on (the professionalism thing again, much more-so than automobile drivers). I think OP was asking more-or-less about taxiing aircraft, which is a case where brake lights would be more applicable, but still not necessary.

Oh, I completely agree that they'd be useless on an aircraft. It was the "brake lights aren't necessary on road vehicles either" that I would dispute. Road vehicles have sub-second reaction time requirements in many cases. Brake lights very much are necessary on road vehicles, especially when driving on highways in heavy traffic, even disregarding people who aren't paying attention or speeders.

@reirab Oh I see, perhaps it's better said: "brake lights on road vehicles wouldn't be necessary under the same conditions..."

I think "no aircraft should be traveling on the ground (taxiing) at such a velocity that stopping in a short distance is a problem - nor should they be following another aircraft too closely (regulations/airport rules govern both taxi speed and following distances)" is a circular argument. These speed limits are likely written as such with due consideration that aircrafts don't have brake lights. If aircraft have brakelights as standard, it's likely the speed limits would be set higher and minimum stopping distance lower such that aircrafts without brakelights would be considered unsafe.

@LieRyan No, taxiing aircraft have those speed limits because they're much less maneuverable than cars and can't stop nearly as quickly. Aircraft are not designed for cornering like cars are. Try to take a turn at 45 mph (let alone 80 mph) in an airplane and you'll have a wingtip on the ground.

The speed limit for taxiing aircraft is human walking speed.  Ground workers should be able to run away from an airplane.

@emory As discussed in What is the maximum taxi speed and who defines it?, it certainly varies depending on conditions (and proximity to ground workers on the ramp is a key condition, but airports would grind to a halt if everyone taxied airliners all the way at human walking speed, unless you can walk at 20-30 knots.

Brake lights are pointless on aircraft because aircraft cannot make fast stops (at least without arresting cables like on aircraft carriers).
Brake lights signal that ground vehicles ahead maybe making fast stops. Following cars can then make their own fast stops based on driver evaluation of distance etc.
Aircraft inability to make fast stops is by necessities of the landing process.  Too sudden braking while landing could flip or otherwise cause loss of directional control.  Remember not all wheels are necessarily touching ground, especially with bouncing and wind gusts. One wheel braking leads to non-Zen results. Plus too firm a stopping action will blow out aircraft tires. Worse there really is not any feedback on braking until tires hit landing strip final time evenly on all wheels and then its too late. So airplane designers remove the landing time hazard by reducing normal braking available (which also reduces weight of brakes and saves fuel/money). Of course the same brakes are in use on taxiways, making slow movement wise.
Furthermore unlike cars, aircraft brakes rely on getting some cooling effects during extended braking.  Landing brakes are optimized for much heavier braking by spreading braking over longer time and distance -- remember plane braking starts at speeds 200-75 mph depending aircraft and much heavier plane weight for wheel size etc.
Brakes on ordinary cars will not melt even during emergency braking. And though tire blow outs are possible, the consequences are generally less than aircraft when each starts at ordinary speeds. Semi and race cars are a bit more like aircraft and do not stop as fast without consequences).

Also remember most ground collisions are not rear-end accidents within steadily moving traffic. The vast majority of collisions are due to wrong turns at incorrect intersections into lines of traffic or even onto active runways which are not even looking for that intersection to be in use. Brake lights would not help as nobody is behind colliding planes.
(Ground control normally uses very few of airports possible taxiway turn points on any given day -- fewer = simpler.)
Where rear-end collisions do happen its almost always the same as cars at a stop light that just changed. Usually no time for brake lights to come on or plane behind to react -- once the guy behind guns it way too fast for the conditions (and usually regulations). Usually the guy in front simply does not accelerate as much or as long as expected by the guy behind -- front plane brake lights never would have come on in time even if equipped.  Similarly sometimes fog is a factor that makes allowable acceleration hard to judge. But like with cars, fog also tends to negate the value of brake lights except to confirm what you hit was not a building.

I'm not convinced that "fast stops" is part of the story here. Sure, the plane in front of you may not be able to stop quickly, but in that case neither are you, so the reaction time you need to avoid ramming him is the same. I would much rather believe an explanation that says planes taxi with enough distance between them that you have time to notice directly that the guy in front of you is slowing down before you engage your own brakes.

Pilots are required to taxi at a speed consistent with being able to stop safely and are generally taxiing in trail so are not going to run into one another.  Most commercial airliners also have maximum straightline and turning seeds defined by their operators.  As these are generally the same - planes are not going to run into each other.
Most accidents (usually wingtip touches) occur when pilots in a rush cut corners instead of staying on the designated taxi line - and so wingtip clearances are lost - on in the generally unmarked non-movement area (where planes DO move - just not under ground control) and pilots are maneuvering to make gates or depart among the jetways, tugs, baggage carts and the like which are SUPPOSED to be moved out the way.


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Why did the Ju-87 Stuka have a siren?
Why did the Ju-87 Stuka have a siren? Was this for purely psychological reasons or did it help the pilot in some way?

This might also go well in http://history.stackexchange.com/

Funny sidenote: That siren sound was so popular with movie makers that, to this day, many people think that any diving (or crashing) plane makes that particular noise...

@DevSolar yeah, I noticed that. Especially in video games.

the siren caused fear into the enemies, which is why it is the most famous ww2 aircraft.

Wikipedia:

The B-1 [variant] was also fitted with "Jericho trumpets", essentially propeller-driven sirens with a diameter of 0.7 m (2.3 ft) mounted on the wing's leading edge directly forward of the landing gear, or on the front edge of the fixed main gear fairing. This was used to weaken enemy morale and enhance the intimidation of dive-bombing. After the enemy became used to it, however, they were withdrawn. The devices caused a loss of some 20–25 km/h (10-20 mph) through drag. Instead, some bombs were fitted with whistles on the fin to produce the noise after release.

So, yes, it was purely psychological and actually hindered the pilot by reducing air speed in ordinary flight and they were removed when they stopped having the psychological effect.

Reducing airspeed is actually kind of helpful in a dive - when you're heading for the ground, even a few km/h can be the difference between pulling up and wiping out. Note that some aircraft of the time had dive brakes to slow them down when dive-bombing.

@anaximander: The Ju-87 have massive air brakes that control airspeed during dives. Compared to the airbrakes the effect of the siren was insignificant. But the siren did have noticeable effect on level flight.

Given the way the StuKa was employed, close to the front lines from forward bases, the impact on level flight wasn't really relevant. Adding 1-2 minutes to the time to get to target isn't bad. And they weren't going to have to dogfight, they were never designed for that. Saving resources for use elsewhere was probably a bigger factor in not fitting them on later models.

@jwenting: While they were not designed to dogfight, they still had to evade enemy fighters and being slower makes them more vulneareable. And they were slow and thus vulnereable even without the sirens.

@jwenting: A drag effect taking 5% off your top speed makes it easier for the enemy to intercept you, or aim at you with flak. It lengthens the time you have to spend over enemy territory. It increases fuel consumption. It decreases your climb rate, both after take-off and when coming out of a dive (when you really want to get back to altitude quickly, after all you just dived on a military target, and small-caliber flak usually takes a dim view on that). Quite significant points, and obviously, the Luftwaffe thought so as well.

@DevSolar as the Germans at the time the sirens were removed were operating under air superiority, I seriously doubt a negative effect on their ability to evade enemy fighters was much of a factor. Neither the Poles, the Dutch, the Belgians, or the French or Danes had air forces that could threaten the Germans over the battlefield.

@jwenting: While that statement is correct on the strategic level, it doesn't help the individual Ju-87 that encounters an enemy fighter. Even a biplane would be a threat to the basically helpless Ju-87. Also note that air superiority doesn't help (much) against AAA, while speed does. "Once the enemy became used to it", the siren was no longer effective, significantly reduced combat performance, and gave the enemy additional warning, so it was removed. You don't put on aerobatic smoke trails just because you have air superiority either (unless you're playing War Thunder)...

@DevSolar of course, but such decisions as to change the design of an aircraft are made at higher than tactical levels. Of course it's quite feasible that units in the field removed the sirens of their own accord when they found them a hindrance, and reporting that back up the chain eventually led to their removal from new production aircraft.

The psychology behind it helped the pilot ... panicking enemies doesn't make for very good shots, they're more likely to miss you. They're also more likely to just drop flat on the ground rather than dive into cover or try to shoot back at you.
And that was pretty much the idea. Get the enemies to become disoriented, panicky, so they're less efficient fighters and easier to defeat by both you and the ground forces you're supporting.

Funny enough, I remember a quote from a British artillery soldier serving in North Africa, on whom the Ju-87 had the opposite effect. "You just ran a couple of meters away from your gun emplacement, and you were safe. They never missed." ;-)

Another reason for the siren is that during the first years of WWII most army's ground transportation was horse drawn. You freak the horses and the unit does not move.  The French, Polish, and Russian armies used primarily horse drawn transport. The British and American armies used trucks.  A truck can't freak out like a horse.

Excellent point, I hadn't even thought of that.

Horses were actually used in greater amount by the German themselves. Confirmed here.


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When taxiing a taildragger across a kerb, is it best to cross straight-on or at an angle?
The grass taxiways at my local aerodrome are sometimes crossed by hard surfaces. Where they cross, the levels don't quite match, so there's a bump as you cross: not quite a pavement kerb, but still a sudden change in surface height.
What's the best way to cross these safely? Crossing straight-on carries the risk that the mainwheels will both stick against the ledge, lifting your tail and in extreme cases maybe causing a prop strike; like trying to cycle up a kerb and going over the handlebars. Crossing at an angle makes sticking less likely, but it rolls the aircraft slightly, and in a low-wing airplane you risk touching a wing-tip.
What's the best way to balance these risks and safely cross the kerb?

Is it possible to put some kind of support to make level difference less? Maybe a sand bag or some pipe so the cross is lower or less vertical?

Opinion: Taxi diagonally to minimize nose-over risk, if the wing tips are too close to ground, don't taxi there. Pull the plane straight over the step manually in this case, tail first.

The rule I was always taught is to cross any 'step' - up or down - at an angle with the elevator full back:

It minimizes the chance of a prop strike, which is much more expensive than a wingtip strike
When going 'up', you avoid having both wheels up against the step at the same time, which usually means you need a burst of power to get over it, which could lead to sudden acceleration and sharp braking
When going 'down' you avoid the aircraft dropping down suddenly, with the same risks of strikes or an increase in speed
Lifting the elevator reduces the chance of it striking

There may be some differences for specific aircraft types, but I've always followed that advice and never had a problem. I've also never seen an aircraft get close to a wingtip strike doing this, but I suppose it could happen if the step is large enough. Although in that case you might want to just find another taxi route.

This is true of both tricycle and taildraggers.


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Do some airplanes have weighing scales on the landing gear?
It seems to me that takeoff weight is an important piece of data, and if one had weighing scales between the wheels and the aircraft body, one could precisely determine it. However, searching the internet, there seem to be no scales and cargo/fuel/passenger weight is estimated by adding up what is brought on board. Why aren't scales common? And are there any commercial airplanes that have them?

Yes, such system exists, for example the Honeywell WBS.* It was developed during the sixties and installed as an option on the Boeing 707-300 freight aircraft. Other aircraft that had a similar (optional) system include the L1011 and Boeing 747.
It is mostly found on freight aircraft because they have a less predictable load distribution (centre of gravity) than passenger aircraft.
The reason they are not common is that they add cost in the form of installation, weight and maintenance. While quite accurate when in good condition, the reliability of the weighing systems used to be poor, which probably contributed to the fact they never became wide spread.
Because crew are commonly operating on several aircraft types these days that have take-off weights of more than 100 metric tonne difference (e.g. A330 and A340, B747-400 and B747-8) there is an increase in take-off weight confusion related incidents. This, combined with the fact that systems are becoming more reliable, makes it likely that these weighing systems will be used more in the future.

* An advert for it in a 1987 Flight issue.

It might be interesting to note that at least Airbus (A320 and all newer models) can calculate weight from aerodynamic performance once airborne and will issue warning if it differs from the value set in FMS by more than specified tolerance (4 t for A320). It is however somewhat late if you are overweight.

The C-130 has such a system, and I'm pretty sure the C-5 does also.

Simple answer
For one thing it will not work because of wind: Once you put wings on a fuselage, you will need to bring that airplane into an enclosed hangar for the scales be accurate.
Mind you, this is exactly what being is done whenever an airplane is being weighted for mass & balance purposes, about every three years: enclosed hangar and massive scales under the gears. Doing it on a daily basis in an already crowded airport is not an option.
Complex answer
What you really need to know for your a/c is mass, not weight. Also, you'd want to know the mass distribution inside the a/c, not just to calculate the center of gravity (which a scale can also do), but also to make sure that load limits are respected in each section (which a scale will not do). Adding and removing numbers on a load sheet works pretty good for this purpose, as does estimating passenger weights and luggage as an average, although there are talks that those averages need to be increased lately.
Even if you eventually found a way to scale each airplane before takeoff, in a controlled environment, the extra costs will never be justified since you basically improved on something that works.

The FMS could calculate the real value. The lift is proportional to the pitot tube reading and angle of attack and therefore known. In fact Airbus systems can check the weight from these values when airborne.

Even in older jet transports that lack an FMS, you can go into the tables and see what the weight is for a given altitude/mach/temperature/fuel flow. Of course, this is once you are in the air at which point the fact that you are 30,000 lbs heavier than you thought you were at takeoff is of little value other than to alert you to the fact that you're probably going to have to stop for fuel before reaching your destination.

@JanHudec That assumes that the wind is uniform across the whole aircraft. But a stationary aircraft (especially parked near a building) isn't likely to experience anything like uniform wind.

"What you really need to know for your a/c is mass, not weight."-- unless we are designing our system to compatible with interplanetary travel, this is no issue.  On planet earth, it's a simple matter to calculate mass from weight or vice versa.

I'm sorry but I don't buy it. Surface winds won't affect that much the final weight of the aircraft. Plus the system is not meant to be used as source of weight data, it's just another step of redundancy. If there is a big discrepancy between the loadsheet and the measured weight a warning should be issued.

On some newer B747, there is a weight indication near the maindeck door. I seem to remember Atlas Air aircraft having this. This would probably have its sensors somewhere in the landing gear.
It was a big LED thing and showed you the current weight of the aircraft, e.g. 340.5 (thousands kgs). When a pallet came in it would show a corresponding increase in weight, so if a pallet weighing 3000kgs came in the weight would now show 343.5.
It was never used for calculating the weights of the pallets in the airports I worked from but I understand that Atlas does a lot of operations for the military in some dodgy areas and at these airports this device helps verify that the weights are not too far off.


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How do the Beech Bonanza's ruddervators work?
How do the Beech Bonanza's ruddervators work? When the yoke is pulled completely back, is it possible to use rudder?

I should hope so, otherwise I don't see how it got through cert the first time

@ratchetfreak: That's not that obvious. The controls can't cross-limit each other within normal operating range, but if they do at the extremes, it allows higher deflection of each.

In the Bonanza, a mechanical mixer controls ruddervator movement based on pitch and yaw commands. Here's a typical V-tail mixer (this is not of a Bonanza though):

(source: eaa1000.av.org)
There are two rods extending off to the left of this photo that connect to the actual ruddervators. Rightward motion of the top rod (due to either rightward motion of the entire mixer assembly due to a pitch command, or clockwise rotation of the assembly due to a yaw command) will deflect the ruddervator one direction; leftward motion deflects it the other direction. Similar for the other ruddervator connected at the bottom.
I can't completely answer the second part of your question, whether yaw authority is reduced when pitching or vice versa. It depends on where the limit stops are installed in a Bonanza. If the stops are set on the ruddervator side (left side in photo above, so that the mixer's range of motion is limited by its leftward connections), the amount of available rudder will be reduced when pitching. (Sorry I can't answer that part of the question, but I thought the information about the mixer would still make a useful answer.)
The airplane is obviously designed so that sufficient authority is available in all situations. (This means making the two fins of the V longer than those of a traditional horizontal/vertical stabilizer design so that similar control surface area is available.)

A paragraph in Flying the Beech Bonanza explains the ruddervator operation:

The following facts from the Shop Manual for the V35B illustrate how
  the control mixer and ruddervator stops allow differential ruddervator
  displacement. With full up elevator and no rudder input, the left
  ruddervator will be 22 1/2 degrees up. With full right rudder and
  elevator neutral, the left ruddervator will be 23 degrees up. And with
  full up elevator and right rudder simultaneously, the left ruddervator
  will be 44 degrees up. By contrast, the elevator of the A36 is limited
  to 23 degrees up and 20 degrees down, while the rudder is limited to
  25 degrees left or right.

TL;DR On the Beech Bonanza, the yaw and pitch inputs are added, so that full back on the yoke gives about 22 degrees of ruddervator, and adding full right rudder would add 22 more degrees for a net result of 44 degrees up of ruddervator on the left.
I assume that the other ruddervator would be at 22 degrees up, though of this I am not sure.

I would assume it will be centered, because pitch command adds 22 up and yaw command adds 22 down for a net result of 0. Because from how the link works, the pitch command adds the same displacement to both and the yaw command adds exactly opposite displacements.

@JanHudec ah ok

@JanHudec hmm, that doesn't seem right... where would the elevator lift come from?

If you pull elevator up and rudder left the resulting command should be diagonally up left, so the right ruddervator is orthogonal to the desired moment and fully deflected and the left one is parallel and has nothing to do.


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Why weren't the rotor tips of the Djinn directly fed from the turbine's exhaust?
The Sud-Ouest Djinn seems to be pretty much the only tip-jet helicopter to have any sort of commercial success. It used a turbine to drive a compressor, which itself fed slightly warm air to pipes in the propeller blades, which itself exited at the tips, making the propeller turn.
This patent from the 90's says that warm air would be more efficient, as exhaust efficiency is limited by the speed of sound, and hot air has a higher speed of sound. As such, the patent is about putting a heat exchanger between the turbine exhaust and the air compressor exhaust.
But then, why didn't they simply plug both exhausts together to go drive the tips, similarly to a high-bypass turbofan? Why simply evacuate the turbine exhaust instead?


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Why is the wrong explanation of "air travels a longer distance and creates a lift" so popular?
When I was learning for my license, one of the first diagrams I remember was about the wing profile. The air going around the wing and on the upper side it has to travel a longer way, thus generating lower pressure and bang, plane is flying.
Same explanation already back at school.
See my other question: if the theory was right, why can planes fly inverted?
So here's the follow up: why is this wrong theory so popular and still part of books?
Wouldn't it make sense to teach students how a wing really works? I mean just look at any RC plane meeting - you'll be amazed what weird designs are capable of flying if there's enough engine power.

Because it's simple enough for a fifth grade to understand.   :-)  Oh, and I usually say that if you have enough power that you can make a plate fly.  Also, when considering the explanation, think about aerobatic airplanes with symmetrical airfoils.  They shouldn't be able to fly either!

But it's also simple to say that storks deliver babies. That doesn't mean it's correct.

I never said that it was!  :) (and yet there are still people who believe in storks too....).  In all seriousness, the "real" reason that wings produce lift is a terribly complicated subject with a lot of different factors, and the average pilot simply doesn't need to understand it.  On the other hand, when someone asks a pilot what makes an airplane fly, it sounds better than "magic" or "I don't know, it just works".

@Lnafziger If I sit in a piece of plywood and Oracover, 10000ft high, "magic" is what describes it best. :-)

A link to a source that explains why this explanation is wrong would be great, especially for people not familiar with the subject. I'm not saying you're wrong, but it would help to understand the answers better.

See also http://aviation.stackexchange.com/questions/466/how-do-i-explain-what-makes-an-airplane-fly-to-grandma

I think this might need rewriting - as it stands, it's basically asking for opinions, which means there can't be a right answer. I love the topic, but I think it's a matter of splitting this up into various sub-questions. Perhaps this is a good Topic of the Week idea?

This answer (not the accepted one by the way) shows some of what you would have to do to give a "real" explanation of lift:  http://physics.stackexchange.com/a/77735.  NASA also has a webpage about the different explanations and what is wrong with them:  http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html.  Wikipedia also covers it nicely: http://en.wikipedia.org/wiki/Aerodynamic_lift

@Lnafziger Symmetrical airfoils don't generate lift without angle of attack, so that doesn't really discredit 6th grade approximation. Since with angle of attack, you move the stagnation point, making one side longer than the other.

Along the lines of weird designs, there's the old re-entry prototype NASA M2-F2 (unpowered) and M2-F3 (rocket engines), where the "longer" side (bulge) is on the bottom. Also the tail is blunt (that's where the rocket engines go), no sharp trailing edge (Kutta condition ). The lift to drag ratio is low, but this is a re-entry prototype, so a high lift to drag ratio is not a goal, and the space vehicle / aircraft has to deal with hypersonic speeds. Link to youtube video https://www.youtube.com/watch?v=qxe0Do5Jleo .

This https://www.youtube.com/watch?v=zp1KzGQdouI shows that motion/lift is possible without Bernoulli.

Long story short is that both Newton's third law and the Bernoulli's effect are two different ways of explaining the same phenomena. Accurate equations have been written to explain both. Newton's third law, the air being forced down and forcing the airplane up, is actually the effect of lift though not the cause. The cause of lift is the change in pressure.
The falsehood that is taught is usually that the two little air particles actually meet up at the same point downstream at the trailing edge of the wing at the same time. This is completely false. In fact, if you were to actually track two air particles, one over the top, and one across the bottom, the one going over the top of the wing will probably arrive much sooner than the one on the bottom! [Even though the distance IS longer] It picks up that much speed. Also they don't actually really meetup again afterwards at all.
The real pivotal relation (which I learned in my Advanced Aerodynamics class at ERAU using John. D. Anderson's book Intro to Flight) is the Kutta-Joukowsky theorem. Taking the time to explain this to a Private Pilot student would probably be a waste of your time and theirs but I will sum it up here anyway to be fair to the question. I will assume incompressible flow because after about Mach .3< it starts to get more complicated.
The Kutta-Joukowsky theorem takes the integral of velocity times the cosine of the incremental angle of the distance along the closed curve. This is a quantity called circulation. The lift equation is then formed as lift equals density (altitude basically) times velocity times circulation. So if you really want get in-depth here is an article from MIT that explains potential flow theory.
What you will find is that the cause of lift is indeed directly related to Bernoulli's principle in that the change in pressure is what creates the lift. However it has nothing to do with particles meeting up at the trailing edge because they never really do meet up. This doesn't discount Newton's third law either: lift can be explained that way but it is the effect of lift, not the actual cause. And yes, like you mentioned, even a flat-plate for example can create lift when angled right in a wind tunnel.

Would it be reasonable to refer to flat plate lift as direct lift and that produced by wing differential pressure (Bernoulli) as induced lift? Also, thanks for the two references.

The curved wing and a flat plate both create lift in the same manner. It's actually drag that is reduced more by the curved wing. Although to be fair keeping the boundary layer attached longer allows for more lift. The shape of the wing is more for keeping the airflow attached longer. Generally you want more INVISCID flow but it is actually the viscous boundary layer that keeps that inviscid flow attached. So the shape of the wing becomes a balance of creating the smallest boundary layer that can still hold the flow without getting airflow separation (stall).

I should add that much depends on the aircraft and it's mission (aerobatics, training, fighter, airliner, crop duster, etc..)

The lift produced by a wing is exactly equal to the mass of the air deflected downward by the wing times acceleration imparted to the air as the wing moves forward.
Newton's second law is why wings produce lift.  Bernoulli's equation is derived from F=MA.

That is correct.

@p1l0t I don't buy the causality arguments here. If 'the change in pressure is what creates lift', then what causes the change in pressure? You cannot simply say 'Bernoulli' or 'Kutta-Joukowsky' because the equations are agnostic about causation, and anyway you would have to explain why they apply in the situation of a wing moving through an otherwise unconstrained air mass. All chains of causality lead to Newton, and to lift being the reaction to the wing's downwards acceleration of the air it passes through. You need hydrodynamics to explain the details, not the root cause.

The best part about science is that it is still true whether you buy it or not. Anyway I think I explained the difference between the cause and effect rather well and included some great sources for further reading. You can try and say the pressure change is an effect of something else which is an effect of something else etc.. etc.. but that could go on forever. My point is still valid. Also I didn't just SIMPLY say 'Kutta-Joukowsky' I explained it as best I could (an entire paragraph) and cited an article from MIT that explains it further.

@sdenham: You need fluid dynamics to explain that the wing deflects the air downwards in the first place.

This is the same argument I always make. I get annoyed all the time with people trying to use this as a gotcha question. I used to design blades in jet engines and they most definitely had a "suction" side and "pressure" side that created the lift. Of course they also changed the direction of the flow, but that was always seen as an "effect."

This https://www.youtube.com/watch?v=zp1KzGQdouI shows that motion/lift is possible without Bernoulli.

@cibercitizen1 Wrong. (nice video though) A flat board still causes changes in pressure.

@p1l0t Thanks. Well, I think that pressure is higher on windward just because wind hits this side; and there is no wind movement on leeward.

@cibercitizen1 I'm not sure what you mean by no movement. The concept of a flat plate and a curved wing are the same. The flat plate is just WAY less effcient. If you are making lift it's because you're creating a pressure difference. The only difference between Newton and Bernoulli is one explains the cause and the other the effect. Both are accurate ways of describing (the same) lift. If you had no movement of air on the top (or a mostly static turbulence or something) the wing would be in a stalled condition and not generating lift (or pressure difference).

@p1l0t Hi. By "no movement"( in the video), I'm trying to mean that on the leeward side, the telltales (the black threads) are totally down, thus showing that no air is flowing on that side of "the sail". My doubt is: no wind motion on leeward, then difference of pressure no due to wind motion. Then motion is due to totally to wind DEFLECTION on windward. Well, don't lose your time too much on this.

@cibercitizen1 Just because the tell tales aren't moving doesn't mean that there is not a pressure difference.

@p1l0t Agreed. But it shows (I think) that the pressure difference is not caused by a phenomenon on leeward, and much less by fast air creating a low pressure zone.

@cibercitizen1 Not necessarily. There is something called a turbulent boundary layer. The air doesn't have to be 'fast.' The pressure simply has to be different. If you create a difference on one side and not the other the air will naturally want to stablize. Also using a hairdryer is kind of a bad experiment because you are already pushing (VERY HOT) air towards the 'wing.' People standing at the beach at St. Maarten still go flying from jet blast and they aren't wings... Has nothing to do with how a wing works. Also the vehicle is moving before the video starts so could be an illusion.

@p1l0t The video is not fake. You can replicate the experiment.

@cibercitizen1 Yes well I can blow anything off a table with a jet engine. What does that have to do with how a wing generates lift?

@p1l0t The dryer is simulating a sailing course (close-hauled) where the angle wind boat-axis is the lowest. This is: "the pushing on sail" component is great at any other course. Anyway, IMHO the video shows motion with no airflow attached at leeward.

@cibercitizen1 What does that have to do with how a wing works?

@p1l0t The relationship would be that the main cause of lift is air deflection per-se. And differences in pressure is a consequence of air deflection; and not the other way around.

@p1l0t A wing and a sail are the same.

@cibercitizen1 Except that a wing only gets a free push from a strong updraft, it's designed to make its own lift, not really to take advangtage of an external push like a sailboat going downwind which is taking more advantage of drag that is going in the direction it wants to go. An airplane can't reasonably do that.

@p1l0t Of course, that's clear. That is the reason for the chosen courses in the video and thus the dryer position related to the wing.

@cibercitizen1 Right and that's fine for a sail but that is not how a wing works. Drag is generally bad in an airplane, we try to avoid it. It's like having a hull full of barnicles. We are trying to move relative to the AIR not the water. A sail can use drag going downwind if it helps them going the way they want relative to the WATER. I fly and sail. They are very similar but also different.

Wouldn't it make sense to teach students how a wing really works?
No, not really.
Ask any (good) CFI and they'll tell you that there are certain topics that a student really needs to understand properly.  Examples:

What's a stabilized approach and how do you fly one?  (A disappointing number of students tell me it means holding the same airspeed all the way down)
Why do we clear the prop area?  (You'd think this would be too simple to screw up, but there's been more students than I've got fingers on my throttle hand who haven't yelled "clear!" until they're already cranking the engine.)

And so on.
How a wing really works is not one of these topics - the consequences of misunderstanding a stabilized approach are that you screw it up and your landings are terrible (or even dangerous).  The consequences of misunderstanding prop safety are that someone loses a hand or dies.  The consequences of misunderstanding how a wing generates lift are...well...the wing keeps flying anyway.
Now, if the student is an aerospace engineer, they'll need to know the real story, but for a pilot, they can continue in their ignorance for their entire career and never be negatively affected (unless they meet an aerospace engineer in a bar and get into a fight).
To extend the point, I myself tell students that to properly understand GPS, you need to get into the theory of relativity, but for a functional but incorrect understanding, you can think of it as "DME-in-space".  It's very wrong on several levels, but it's enough to satisfy the needs of that category of student - same as the wing pressure-differential explanation.

I agree with this answer, but it would be nice if there were an "easy" description of how a wing generates lift that wasn't so obviously wrong, and couldn't even possibly explain several common scenarios.  I mean what else have they been lying to us about all of this time???  :)

@Lnafziger - Well, for one, the real reason for TBO time is to swap out the hamster on the wheel in there.

Haha, that must be one strong mutant hamster!

I also agree with this answer, but I did take a shot at explaining lift that wasn't so obviously wrong in my own answer with some links for further reading. Still, gave him the vote up though. As far as students they need to know that they can pull up for more lift until the critical angle and no more. See what I did there.

Upvoted both of you.

To properly describe something to that detail should not be necessary. If you truly understand something, even GPS, you can describe without math. GPS works because of highly accurate clocks measuring the time it it takes for something to happen, a radio signal in this case, and done multiple times from multiple places really fast. The clocks are really far away to make both the position more accurate and the math easier. They are also far away so they can use fewer of them.

@RowanHawkins - You are right. Everything can be described without math.  Not everything can be understood without math.

"more students than I've got fingers on my throttle hand who haven't yelled "clear!" until they're already cranking the engine." - Not only students.  I've seen more than one licensed pilot yell "clear" and then, without allowing the necessary time for anyone to hear and move out of the way, cranking the starter.


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How can I calculate takeoff distance in a generic way?
I want to build a generic performance app.
For many of the aircraft the only available method is using the takeoff charts manually (I'm not referring to the more simple-to-calc short field charts but to the charts which consider also the wind components).
Is there a way to convert these charts into numbers that allow me to calculate the output once certain parameters (weight, OAT, PA) are entered? Is this data available somewhere?
Or do pilots do it with chart and pencil for every flight?
(Not a pilot myself.)
example of takeoff chart :

If the chart is straight line i believe you can calculate the gradient and work from there. Do you have any chart on hand?

I edited the original post with an example

These are usually also available in tabulated data form, but not always. Usually you can convert them to data points, I had made a program quite a while ago that would load in an image then you would click to define the two axes and click on the lines to generate a chart.

Welcome to aviation.SE! I just edited your question a little, but I don't completely understand what you're asking. Are you asking if it's possible to calculate takeoff distances for any aircraft based on a few generic parameters? Or are you asking how to convert a performance chart for a single, specific aircraft into a mathematical formula?

Thank you ! tabular performance charts enable me to enter their data into excel (for example) and create a formula to get the results.The other chart type (one of the users commented they are sometimes called a "run-around-chart") require manual calcuation , using lines , as per the example I attached.My question is - is there a way to have these charts as tabular data as well ? since these are graphs I assume the data exist somewhere.

"I just edited your question, but I don't completely understand what you're asking"?.  Why not ask first? Yuval, what you need for your wind direction factor would be distance data for an accelerating aircraft (on take off).  You would then graph distance to 5 mph, 10 mph, 15 mph etc.  These distances are what you "save" taking off into a headwind.  This factor would go into your formula for takeoff distance. But before publishing it, it needs to be VALIDATED with testing to be reliable.  Good luck!

One way would be to calculate the total energy change needed for a take-off and then to calculate how long the engine has to run to provide the aircraft with that energy. Once you have time and speed, calculation of distances should be easy. Calibrate with the charts if needed.
The total energy is the sum of mass times speed change squared divided by two, weight times elevation gained (or lost) from runway slope and weight times the height when the take-off is complete. The speed change can either be from static to lift-off speed (plus or minus wind speed) or to the multiple of stall speed required by your definition when the take-off is complete.
While at the start of the take-off sequence drag will be negligible, you need to reduce net thrust by the drag of the moving aircraft. This is generally the hardest part, but if you are willing to accept some error, a simplified drag model can be used which assumes friction and rolling drag while the aircraft accelerates, then adds induced drag as the aircraft rotates and reduces overall drag as the aircraft accelerates after take-off. Also, don't forget to model the speed dependency of thrust as well.

My gut feeling is that while this is a very valid first principles approach, there would be too many assumptions included for it to be safely used in real operations when not based on certified or at least manufacturer-endorsed data. For example, propulsion efficiency, landing gear drag, rolling resistance are all important factors which are not normally well known outside the aircraft manufacturer except when specifically published. Not my downvote despite not agreeing :)

@CptReynolds: That is why I propose to calibrate the mathematical model using existing take-off charts. I've done this myself and generated more precise data than an actual flight test because measurements in flight test have their own margin of error. In other words: I speak from experience. The downvote was by someone who simply did not understand the concept.

That is a very good approach, and I agree re. flight test inaccuracies. Will supporting the model with takeoff charts allow identification of individual effects, only the combined total effect of which is in the charts (I.e. thrust and drag at low rolling speeds are both unknown, and from the chart you can identify acceleration but not individual forces)?

@CptReynolds You are right, the charts only give you the sum of all forces. But there should be charts for different flap settings, wind speeds, elevations, temperatures … in other words, enough to calibrate the model for all those parameters. And the goal is to arrive at generic take-off distances. In order to determine all drag contributors, I would recommend some serious bookkeeping.


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How does retracting the gear affect weight and balance?
In many of the POHs, in the W&B section it is indicated that there is a moment change due to gear retraction. For example :
Moment change due to gear retraction +780 in-lbs.
Two questions :

If I understand correctly, to simulate a gear retracted scenario I only need to add 780 to the total moment (sum of moment for the empty weight, crew, passengers, baggage etc...) while calculating the W&B. Is that correct?
In the majority of the POHs the C.G. envelope limits are based on gear down (fwd and aft).I saw one aircraft where it states the aft C.G. for both gear down and gear up - does it mean there is a different C.G. envelope for each case?

The aircraft in question is CJ-6A, please note the footnote in the image below

What poh are you talking about?

Sorry , I'm not clear with your question.I mean the aircraft operating manual if that's what you mean.

I know what a POH is, I'm wondering exactly which one you are referring to? For example I can't find any reference to a moment change in the POH for a 172-RG. I also don't think you would add anything, you need to move it, the weight isn't changing, the CG is moving.

I see it now, the CJ-6A, I didn't see it at the end of your second question before...

You have a many aircraft with moment change due to landing gear retraction.I will send you few examples if you need.The moment is added to the total sum of moments and then devided by total aircraft weight to get the loaded aircraft c.g

Btw - also the 172-RG has moment change due to landing gear retraction.Look at section 2 - Limitations, you will find this info under "CENTER OF GRAVITY LIMITS"

Yes the +780 inlb is the increase in the total moment aft of datum (I'm assuming it's the firewall) due to the center of gravity of the gear strut moving aft when it retracts.  It's like you had a lead weight at your feet and you moved it a foot or two aft.  Some retractable gear airplanes don't account for this but the Nanchang does seem to have a very long nose gear with substantial mass, so it looks like they decided they needed to take its movement into account.
The aircraft's CG envelope is a function of pitch stability at the aft limit and tail authority at the forward limit at various loadings and doesn't change.  You are concerned with the actual CG location relative to the limits and there shouldn't really be two envelopes, just two CG location values for any particular load case, a gear up one and a gear down one, that reflects the 780 in/lb influence of the nose gear's movement on the CJ-6.
Since gear retraction moves the CG aft, your main concern is that the actual CG location respects the potential two worst case conditions; that is, aircraft CG gear up is within the aft limit, and aircraft CG gear down is within the forward limit.
That's how it should work and if there are actually two CG envelopes, it suggests that there are aerodynamic effects of gear extension on pitch stability and/or tail authority that were uncovered in flight testing, and that go beyond just the CG of the nosewheel moving forward.  But in that case you would just expect to see a CG envelope that is more restrictive than it would otherwise be, to cater to the worst case possibilities, not two separate sets of forward and aft limits.

Thank you for the detailed and clear answer John.

I edited the original question and added a photo of the c.g. envelope of the CJ-6A .The wording at the bottom state  the aft c.g. when landing gear is up.This raised my question.Can you explain why they pointed the aft c.g. with gear up? further info - I also have the aft c.g. with gear down and also the %MAC of change due to landing gear retraction (which is the difference between %MAC aft gear down to %MAC aft gear up).Last point - the envelope in the picture is according to aft gear down.

That seems very weird to me.  You would normally take all the variables into account to come up with an aft CG limit to cover the worst case loading and gear configuration, which would be gear up, because if you're at that limit in flight, lowering the gear moves it forward and all's well so who cares.  I think maybe the Chinese/Russians (it's a Yak knockoff) were thinking too hard.

Pure speculation, but could it perhaps be to allow flight with an extra heavy passenger or cargo in the rear seat subject to the limitation of not retracting the gear? Performance on the Yak doesn't improve all that much when you retract, anyway.

That's an interesting thought.  Tandem airplanes that solo from the front tend to have to deal with a large CG movement between 1 and 2 up because all the load variation is aft, so there could be a back seat weight restriction that can be increased if you leave the gear down.

Indeed interesting thought.I managed to fish a POH and I can't find any place where the aft c.g. gear up is mentioned.Maybe someone created the above envelope by himself and assumed that the 0.7%MAC change due to gear retarction should be added to the 23.4%MAC aft c.g. gear down which I believe this is a mistake as the change of 0.7%MAC should be within the 23.4%MAC limit.Thank you all for your great help!


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What is the typical sink rate during a well-executed carrier landing at the moment the main wheels touch the deck?
What is the typical sink rate during a well-executed carrier landing at the moment the main wheels touch the deck?  And how has this changed over the decades?

Possible duplicate of What is the procedure for landing on an aircraft carrier?

from this answer: "At the 90, altitude should be 450ft AGL, and VSI should increase to 500fpm"

A lot. About 3-4 m/s (600-800 fpm). This is the speed at which 'normal' landing gear begin to break.
For carrier landings, there is no flare, so the touchdown speed equals to the sink rate on the final approach. The procedure in the linked question mentions 700 fpm.
We can arrive at a similar figure if we consider the standard carrier glideslope 3.5° (pdf) and the typical approach airspeed of ~120-130 kn. If we allow 20-30 kn for carrier speed and headwind, then for 100 kn (51.4 m/s) closing speed we get 51.4 m/s * sin 3.5° = 3.14 m/s ≈ 620 fpm.

Yep, good answer.  600 was about what we would target.

it’s dependent upon the aircraft in question and the approach speed that they need to use, but assuming a fighter aircraft like an F-18 with an approach speed somewhere in the neighborhood of 130 knots, a typical 3.5° glideslope to impact yields a descent rate on somewhere between 600-700fpm.   The faster the ship is moving and the greater the surface winds it’s steaming into, the lower the vertical speed will be on glide path to touchdown.

A carrier glideslope is 3.5 degrees.  And 6 months later, this answer doesn't really add anything...


text:
When do the lift and drag vectors contribute a force component along a glider's path of travel as seen from the ground?
It is often said that the lift vector helps to propel a glider forwards.  The lift vector has no component acting parallel to the glider's trajectory through the airmass, but in many cases the lift vector does have a component acting parallel to the glider's trajectory as seen from the ground.  Note that for a given airspeed, the direction of the glider's trajectory through the airmass-- i.e. the direction that is exactly opposite to the "relative wind" that is "felt" by the glider-- is not affected by sustained updrafts, downdrafts, headwind, or tailwinds.  But this is not true of the glider's trajectory as seen from the ground.  A glider in a powerful mountain wave updraft may be rising straight up as seen from the ground, while the trajectory through the airmass will still be the normal glide path that would be obtained at whatever airspeed the glider is flying at.
Under what circumstances does the lift vector of a glider contribute a force component along the glider's path of travel (trajectory) as seen from the ground?
Under what circumstances does the drag vector of a glider contribute a force component along the glider's path of travel (trajectory) as seen from the ground?
Likewise for a powered airplane.
Note -- to avoid any possible ambiguity, please be aware that this question is using the word "lift" exclusively to mean an aerodynamic force generated by the aircraft, not to mean rising air.  These are two completely different things.
Note -- the scope of this question is meant to be confined to linear (but not necessarily horizontal) straight-line flight with constant airspeed and groundspeed, at least over the short term.  We're assuming the glider (or airplane) is flying in an airmass that is locally uniform. In other words, if the glider has entered a thermal updraft or penetrated through an abrupt wind shear or flown from sinking air into a ridge updraft or wave updraft, we're assuming that it has been in the new airmass long enough to come into equilibrium, so that net force is zero for the time being.  This is not a question about "dynamic soaring" as practiced by the albatross over the open ocean, r.c. glider pilots flying in loops on the lee side of the hill, someone trying to put into practice Taras Kiceniuk's ideas about exploiting the boundaries between still air and downdrafts as a source of energy, etc.  Those subjects are worthy of an ASE question, or many questions, but this is not that question.

Comments are not for extended discussion; this conversation has been moved to chat.
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In thermals.
More precisely: Every time when the updraft strength increases. The glider will continue on its original path due to inertia while the airflow will have a positive angle when referenced to the path of travel. Now the aerodynamic force will point slightly forward and accelerate the glider.
Experienced pilots use this by pulling more than 1 g when flying into a thermal and less when updraft strength decreases. This helps them to gain some more energy from the rising air.
Drag is per definition the part of aerodynamic forces parallel to the flow direction, so for drag the answer is: Always. With changes in vertical airspeed, the drag component parallel to the direction of movement will merely change with the cosine of the angle between the aerodynamic and the kinetic coordinate systems.
If you insist on excluding changes in vertical air speed, your question will have no answer regarding lift.

"If you insist on excluding changes in vertical air speed, your question will have no answer regarding lift."-- why not?

@quietflyer Because in the absence of wind the aerodynamic and the kinetic coordinate systems are identical.

But there can be a CONSTANT updraft or downdraft.  Locally constant I mean, over the time and distance scale needed for the glider to come into equilibrium (just a few seconds).  Also even in the presence of  a tailwind but no updraft, the lift vector has a component acting along the glider's path of travel (trajectory) as seen from the ground, as noted in the (currently) downvoted answer.  Maybe it will become more clear if I add a diagram.

Any glider is powered in part by its lift vector at all times when in normal flight (as opposed to a loop, roll, or other aerobatics, where a reserve of kinetic energy is used and often partially converted to potential).  The lift vector is always angled slightly forward when in gliding flight.
The energy for this comes from conversion of potential energy (in the form of altitude) into kinetic energy (in the form of forward speed).  Potential energy, in turn, for a glider, is in general supplied by rising air (initially for each flight, some is given by the launch assist -- whether aero tow, ground tow, winch/bungee, or by rolling/running down a slope into ridge lift).
Drag, on the other hand, by definition is always opposite in direction to the velocity vector, so will never have a component that adds to current velocity (though if the glider is, for instance, in a deep stall with tail down, there may be a drag component "forward" in the direction the glider's nose is pointed).
For powered airplanes, there will be times when there's a lift component that acts to increase forward speed (for instance, when descending more or less steeply at low throttle), and times (most steady-state flight) when lift contributes to drag -- which still, by definition, acts against current velocity vector.

I think I want to confine the question to steady-state linear flight.  Would that invalidate anything in your answer?  I don't think so.

Not directly -- but don't forget that in still air, a glider can't maintain level flight for long (it's converting kinetic energy to replace drag losses if it quits giving up altitude).

@Zeiss Ikon your answer is a plus, but the wing is only the lifter/propeller.  The "power" comes from potential energy converted to kinetic energy "falling".  Notice birds have lifter/propellers too, but the "power" is from the muscles, and bird seed is the "fuel".

@RobertDiGiovanni You've almost quoted my second paragraph.  "The energy for this comes from conversion of potential energy (in the form of altitude) into kinetic energy (in the form of forward speed)."

"As seen from the ground" will be the net trajectory of the gliders vertical and horizontal velocity components added or subtracted from the vertical and horizontal velocity components of the air (discounting the third axis for now).
We consider the theoretical uniformly moving air mass and the relative wind the glider creates in flight.  As discussed many times on this site, a perfect circle in the air will look a lot different as a ground track if there is wind.  A glider with an airspeed of 40 knots may be motionless "as seen from the ground".
Logicly, the answer is always, with the caveat that the air mass movement velocity and direction must be considered, and yes, along all 3 axes.
Finally,  one of the keys is to consider that weight is subtracted from any vertical drag  or lift vector components,  the remainder is balanced in the glider velocity and direction with respect to the airmass.

I found this easier to work backward from the aircraft's velocity and direction (starting with no wind case). The horizontal component of the lift vector will match the horizontal drag component.  The vertical lift component plus the vertical drag component equal the weight component.  Net forces are 0 at a given equilibrium velocity.

"Finally, one of the keys is to consider that weight is subtracted from any vertical drag or lift vector components,"-- that is the purpose of drawing the vector triangle, as noted in the downvoted answer.

@quiet flyer something about a Billy Joel record being "cut down to 3:05".  Some people just need it to be short.  Your question is very good and still not completely answered.  Vertical drag may indeed contribute a horizontal component in the direction of flight.  A falling object tilted forward gets pushed forward by the "up draft". Re-read Kampf, an amazing and detailed source of knowledge.

Assuming steady-state linear flight and the other constraints stated in the question--
The idea that a component of the Lift vector is helping to pull the glider forward along the glider's trajectory as viewed from the ground is only true when the glider's achieved glide ratio relative to the ground is better than the L/D ratio (which is also the still-air glide ratio), or when the glider is climbing in an updraft (unless the glider is drifting backwards over the ground along an achieved climb path that is flatter than the direction of the drag vector/ relative wind). These are the only times the that the Lift vector has a forward component relative to the glider's trajectory as viewed from the ground.
This would only happen in one the following cases -- the glider must be flying in:
1) Air that is neither rising or sinking, but is moving with tailwind component relative to the glider's actual heading (not relative to the "course" or achieved ground track-- the distinction comes into play when there is a strong crosswind component.)
2) Air that has no horizontal motion, but is rising.
3) Air that is rising fast enough to offset the degradation in achieved glide ratio caused by a headwind component.
4) Air that is moving with a tailwind component that is strong enough to offset the degradation in achieved glide ratio caused by a sinking (downdraft) component.
5) Air that is rising and also is moving with a tailwind component
To a first approximation, the idea that a component of the Drag vector is helping to pull the glider along the glider's trajectory as viewed from the ground is only true when the glider is moving backwards over the ground-- i.e. when a component of its "course" or achieved ground track vector points in the same direction that the tail of the glider is pointing, and opposite the direction that the nose is pointing.  This can easily happen in strong wind-- the glider can easily drift backwards over the ground.
Strictly speaking this approximation is only true if the L/D ratio is infinite.  To be more precise, we have to recognize that the true criteria is that the Drag vector will help pull the glider along the glider's trajectory as viewed from the ground whenever a component of the actual three-dimensional flight path as viewed from the ground-- not just the "course" vector or achieved ground track-- points in the same direction that the Drag vector is pointing.  Since the Drag vector is parallel to the flight path through the airmass or "relative wind", it is inclined relative to the horizon.  Therefore for non-infinite glide ratios this criteria can be achieved when the aircraft is rising straight up vertically relative to the ground with zero horizontal groundspeed in a strong updraft, or even when the aircraft is creeping forward very slowly over the ground as it rises rapidly upwards.  Also, there can be cases where the criteria is not met even if the aircraft is drifting backwards very slowly over the ground, if it is also sinking very rapidly due to a strong downdraft.  But for reasonably high glide ratios, it's a fairly good approximation to say that the Drag vector is helping pull the aircraft along its trajectory as viewed from the ground only when the aircraft is actually drifting backwards over the ground.
What is really going on here is that we have a closed vector triangle of Lift, Drag, and Weight, with Lift smaller than Weight and inclined slightly forward relative to weight.  Drag is perpendicular to Lift and acting at right angles to Lift, as illustrated in this related answer.  There is no question that net force is zero, and net acceleration is zero, from any inertial reference frame, including the airmass reference frame and the ground reference frame.  But the velocity vector is different in different reference frames-- for example consider the case where the glider is slowly rising straight up as seen from the ground reference frame-- so the issue of which forces are contributing a component along the glider's direction of travel depends on which reference frame we choose.
Note that it is often said that gliders are powered by gravity.  This is always true as seen from the airmass reference frame-- of the three forces Lift, Drag, and Weight, Weight is the only one with any component parallel to the glider's path of travel through the airmass.  But as seen from the ground-- i.e. in relation to the path of travel relative to the ground-- gravity is exerting a force component parallel to the trajectory only in cases where the glider is losing altitude.  If the glider is climbing, then the Weight vector is exerting a force component against the direction of glider's trajectory as seen from the ground, not in the same direction as the glider's trajectory as seen from the ground.  If the glider is flying horizontally, then from the viewpoint of the ground-based reference frame, the Weight vector is exerting no force component along the direction of the glider's trajectory, and is doing no work on the glider.
This means that whenever a glider's velocity vector as seen from the ground is constant and is purely horizontal, the forces exerted along the direction of travel by the Lift and Drag vectors must be exactly equal and opposite.  Whenever a glider is travelling horizontally and the glider's velocity vector as seen from the ground has a component toward the nose of the glider rather than toward the tail of the glider, the Lift vector is helping to pull the glider along its path of travel, and the Drag vector is resisting that pull in a way that exactly cancels it out.  Conversely, if the glider is travelling horizontally and backwards as seen from the ground, then Drag vector is helping to pull the glider along its path of travel, and the Lift vector is resisting that pull in a way that exactly cancels it out.
The Lift and Drag vectors are fixed in their geometric relationship to the relative wind-- Lift is perpendicular to the relative wind, and Drag is parallel to the relative wind.  Furthermore, for any given L/D ratio and Weight value, the Lift and Drag vectors are fixed in magnitude.  The fact that, from the ground reference frame, the force component exerted in the glider's direction of travel by the Lift and Drag vectors varies according to the wind direction and updraft or downdraft velocity, is really just an artifact of the fact that direction of the relative wind is not fixed in relationship to the direction, and magnitude, of the glider's velocity vector as seen from the ground.
The work done by a force is defined as distance traveled times the force component exerted in the direction of travel, and it takes energy to do work on a glider or any other body.  It doesn't really make sense to ask what energy source is responsible for any one particular aerodynamic force component, such as the component of the Lift or Drag vector that is acting parallel to the flight path as viewed from the ground.  Ultimately, as seen from the ground, any NET energy transferred from the atmosphere to the glider, via the combined action of the Lift and Drag vectors, can only come from updrafts.  Only in the presence of an updraft can a glider gain altitude while flying at a constant velocity, regardless of the horizontal wind speed and direction.  Of course, as the glider extracts Kinetic Energy from the updraft and converts it into its own gravitational Potential Energy, the updraft must be slowed by an infinitesimal degree.  The only instance where the glider is neither increasing nor decreasing the Kinetic Energy of the surrounding local airmass is when the glider is travelling purely horizontally, rather than sinking or climbing.
And the ultimate energy source that powers updrafts-- whether they are thermal updrafts or "ridge lift" updrafts or mountain wave-- is the sun.  This power may be conferred either via direct solar heating of the ground directly below, or by complex meteorological processes involving the entire global weather system.
The question also asked about powered aircraft.
Assume for simplicity that Thrust acts exactly opposite in direction to Drag.
In the case where Thrust is less than Drag, the aircraft is exactly like a glider, except we substitute "(Drag minus Thrust)" wherever "Thrust" appears in the explanation.
In the case where the Thrust and Drag are equal, the explanation regarding the Drag vector is exactly the same as the "first approximation" explanation (assuming infinite L/D ratio) above.  And in this case, the Lift vector is adding helping to pull the aircraft forward along its trajectory relative to the ground anytime the aircraft is in rising air, without exception, and without regard to headwind or tailwind.
In the case where Thrust is greater than Drag, then the idea that a component of the Lift vector is helping to pull the aircraft forward along the aircraft's trajectory as viewed from the ground is only true when the aircraft's achieved climb ratio relative to the ground is better (i.e. a lower number than) than the L/(T-D) ratio.  This will require an updraft, or a headwind, or both, and a weak updraft may not be enough to offset a strong headwind, and a weak headwind may not be enough to offset a strong downdraft.
In the case where Thrust is greater than Drag, then the idea that the Drag vector will help to pull the aircraft along the aircraft's trajectory as viewed from the ground can only be true when the aircraft's trajectory as viewed from the ground has a component pointing in the same direction as the drag vector.  For ratios of L/(T-D) that are not too high (i.e. the still-air climb angle is not extremely good), to a first approximation this means that the aircraft is drifting backwards over the ground, but this approximation will not apply well to extremely high still-air climb angles.  An aircraft that could climb straight up at a high rate of climb in still air could, in that same configuration, only move (as seen from the ground) in the direction of the Drag vector in the presence of an incredibly strong downdraft.


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How can I determine the runway number from its true bearing and magnetic variation?
Given:

Runway True Bearing 007°
Magnetic Variation 4°E

What is the runway number (or designator)?

Runways are named after their magnetic headings.
To convert from True to Magnetic, use "East is least (i.e. subtract), West is best (i.e. add)".
If you are standing at this location looking in the direction 007 T, to find the direction you are looking in magnetic terms, subtract the 4 degrees E variation to get 003 M.
This should not just be a rote rule in your mind, but rather should make intuitive sense as you picture the situation in your head --  for example, if you are standing somewhere on the west coast of the US with a Silva-style hand-held compass with the sighting arrow pointing at your target and the big arrow on the rotating bezel pointing to true north, and then you twist the bezel to change the big arrow on the bezel to line up with with the magnetic needle and point to magnetic north, you'll be twisting the bezel clockwise (because the magnetic north pole is in northeastern Canada), and the number under your sighting arrow will get smaller.
Hence "East is least"-- a line to magnetic north pole is, from your position, aimed to the east of a line to the actual north pole, so you to go from True to Magnetic you twist the bezel clockwise, which subtracts from the number under the sighting arrow.
Now just round to the nearest 10 following normal rounding rules, and drop the last zero.  003 rounds to 000 (or 360) which becomes runway 00 (or 36).  Which one of these two choices is it?
Values that round to 360 or 000 -- these are the same thing-- are always designated runway 36, not runway 00.
Sometimes you'll have to go "over the hump" and cross from a heading east of north to one west of north or vice versa-- just add or subtract 360 as needed for the answer to make sense -- for example 10 degrees true minus 20 degrees easterly deviation gives negative 10 degrees but just throw in an extra 360 degrees and you'll come out with 350 degrees which makes sense.  Again you should be able to picture in your mind exactly what is going on here.  If it doesn't make intuitive sense to you, get a Silva-style hand-held compass and practice; it will help you visualize everything clearly.

After all that, be sure to look at a source like Airnav.com as runway numberings are only renamed/repainted very occasionally.  An airport near me, KFIT, is currently under construction to change the runway heading by some number of degrees, and I think I informally heard to lengthen it. One can see the a picture of the change here https://chapters.eaa.org/-/media/Chapters/Chapter-Folders/EAA1454/Images/1432-Nov-2019.ashx?h=409&w=300&la=en  Apparently the shorter crossing runway is closed permanently too.

That's what I thought as well, however, it's BH AIP that makes me confused. Could you check: https://eaip.bhansa.gov.ba/2020-03-26-AIRAC/html/index-en-GB.html
Part 3 Aerodromes (AD) -> LQBZ* ZALUŽANI - BANJA LUKA
For the given variation and true bearing, the runway designator is 01.
The same can be observed with LQPP* POPOVI - BIJELJINA.


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Does the FAA have a document that details each step found in a Component Maintenance Manual?
Is there a standard FAA document type for 'general' maintenance steps that a Component Maintenance Manual (CMM) can reference?
For example:

Once the bulb has been locked into the socket, reference the bulb
  cleaning section in Document XYZ for the complete bulb cleaning
  procedure.

Where can I find Document XYZ?

Welcome to aviation.SE! I edited your question to make it a little clearer, but I might have misunderstood what you're asking. If I did, don't hesitate to edit your question again, or roll back my changes. The [tour] might also be helpful if you're new to the site.

The FAA does have the Advisory Circular 43-xx series, but I've never seen a CMM that references them. Most manufacturers are very risk/liability averse and won't reference anything they don't control.

In general aviation and even working in FBOs, I have referenced AC43.13 to approve repairs that the CMM does not cover. These processes and techniques are approved by the Administrator. In general terms, the FAA tends not to tell you how to meet a requirement but rather gives the requirement then the organization has to meet that requirement through a FAA approved QMS. This process is applicable regardless if you are working with the MIDO, ACO, or FISO. In order to get down in the weeds, you would have to be very specific in your question.
Here is the link to FAA AC43.13 for everyone's review.
https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentid/99861
Best,
Mark

There is a standard for what they must include but not where they are to be found. The standard simply states they they be "available". According to order 8110.54A the "document XYZ" must be available to you and must include the following:

10. Component Overhaul Manual or Section. If the aircraft, aircraft engine, or propeller maintenance information references the use of a
  component overhaul manual, or specific section of a CMM, as the
  appropriate location for the ICA, those applicable instructions are
  incorporated by reference and become part of the complete set of ICA.
  If component overhaul manual information was developed to comply with
  14 CFR § 21.50 then the component overhaul manual, or referenced
  section(s) are part of the ICA. As part of the ICA, it must be
  furnished to the owner and made available to any other person required
  to comply with those instructions per 14 CFR § 21.50. This manual or
  section must contain the following information:
a. Cleaning and
  inspection instructions that cover the materials and apparatus to use
  and methods and precautions to take during overhaul. These
  instructions must include methods of overhaul inspection;
  b. Details on all fits and clearances for the component relative to overhaul;
c. Details of repair methods for worn or otherwise substandard parts with information
  necessary to determine when to replace parts;
d. Instructions for testing the article after overhaul. This should include test acceptance
  criteria;
e. Instructions for storage that identify special containers and required equipment or
  tools. The ICA should also include the environmental restrictions for storage and storage limits;
  and
f. A list of tools and equipment necessary for maintenance and directions as to their
  method of use.